The attempt in the previous chapter to ascertain some of the differences between fabliaux and fables, and to arrive subsequently at a better understanding of the distinctive features of each, was an essentially extensive procedure, taking its point of departure in the texts themselves, and hoping by analysis to identify some features applicable to all members of the respective genres. The investigation in this and subsequent chapters will aim to arrive at an intensive definition by creating a theoretical inventory of definitive structural devices that in some variation or combination are an essential ingredient in all examples of the genre.

An appropriate beginning for a structural analysis is to compile an inventory of the logical exchanges which involve some shift in truth-values, and which therefore constitute a definitive feature of all fabliaux. Most of these exchanges can be assimilated to one of the fallacies treated by Aristotle in the Sophistici elenchi and by the authors of commentaries on that work from late classical antiquity onwards. The Middle Ages knew Aristotle's treatise through the translation of Boethius. In addition, the period from the twelfth to the fourteenth century produced numerous handbooks and treatises on logic which included a treatment of the fallacies, and followed more or less faithfully the Aristotelian scheme of analysis. The most important of these were the Summulae logicales of Peter of Spain, the Introductiones in logicam of William of shyreswood, the De Fallaciis ad quosdam nobiles artistas of Thomas Aquinas, and the Fallaciae of Siger of Courtrai.